Prevent "mark instance as NSFW" from producing hellspawns

What does this PR do?

Prevent "mark instance as NSFW" from applying to boosts. This fixes a bug where boosts by a user from a NSFW instance are incorrectly converted into quotes despite existing as boosts on all remote instances (AKA hellspawns). Local users are able to react or reply to the fake "quote", but those activities are rejected by all remote instances. It's effectively a federation-killer.

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packages/backend/src/core/NoteCreateService.ts

@@ -146,6 +146,8 @@ type Option = {
 	app?: MiApp | null;
 };
 
+type PureRenoteOption = Option & { renote: MiNote } & ({ text?: null } | { cw?: null } | { reply?: null } | { poll?: null } | { files?: null | [] });
+
 @Injectable()
 export class NoteCreateService implements OnApplicationShutdown {
 	#shutdownController = new AbortController();
@@ -412,7 +414,7 @@ export class NoteCreateService implements OnApplicationShutdown {
 
 		if (user.host && !data.cw) {
 			await this.federatedInstanceService.fetch(user.host).then(async i => {
-				if (i.isNSFW) {
+				if (i.isNSFW && !this.isPureRenote(data)) {
 					data.cw = 'Instance is marked as NSFW';
 				}
 			});
@@ -821,6 +823,11 @@ export class NoteCreateService implements OnApplicationShutdown {
 		if (!user.noindex) this.index(note);
 	}
 
+	@bindThis
+	private isPureRenote(note: Option): note is PureRenoteOption {
+		return this.isRenote(note) && !this.isQuote(note);
+	}
+
 	@bindThis
 	private isRenote(note: Option): note is Option & { renote: MiNote } {
 		return note.renote != null;